It is frequently desirable or necessary in performing dental diaqnostic procedures to measure the occlusion, or points of contact, between a patient s teeth as the patient closes his or her jaws. Occlusion measurements are necessary, for example in prescribing and fitting many dental appliances such as false teeth or orthodontic devices. Such measurements enable the user to determine where the teeth first contact each other, disclosing high spots and other useful information.
In order to provide an accurate measurement of the occlusion, an occlusal measuring device must be extremely thin so as not to perturb the normal dental alignment. A sensor must also have a very high spatial resolution to provide useful information and distinguish between contact and non-contact points of the teeth. Additionally, a practical sensor must be safe for oral use and should be capable of being used by non-technical personnel with minimal training.
Until recently, the types of occlusal sensors available to dentists for measuring occlusion have been limited. The most common method of measuring dental occlusion is by means of a piece of carbon-paper-like material upon which a patient bites down. Another occlusal sensor uses a thin piece of plastic to provide an imprint of the occlusion which, when illuminated with polarized light, indicates the points of contact by different colors. Other methods exist for performing occlusal analysis, including wax impressions and casts of a patient's teeth, but these methods are expensive, time consuming, and in general are not suitable for large scale use in dental offices.
Recently, a new contact sensor has been developed which detects points where the sensor is being contacted on opposing sides by teeth surfaces. The sensor is extremely thin, on the order of a few thousands of an inch thick, and can provide high spatial resolution capable of distinguishing between contact points separated by 0.050 inches or less. This contact sensor includes two sets of parallel electrodes which are each formed on a thin, flexible supporting sheet. The electrodes are then coated with a thin, pressure sensitive resistive coating. Two such electrode structures are oriented at approximately right angles to create a grid where the intersecting electrodes cross. This sensor is described in co-pending U.S. patent application Ser. No. 717,532 Now U.S. Pat. No. 4,734,034 for A Contact Sensor for Measuring Dental Occlusion, which is incorporated herein by reference.
In this sensor, the pressure-sensitive intermediate layer provides a high resistance between intersecting electrodes when no external pressures are applied to the sensor. The resistance changes abruptly to a comparatively low value at locations where external pressure is applied by two contacting points or surfaces. The sensor resistance will change back and forth between high and low resistance states as external pressure is repeatedly applied and removed, allowing repeated measurements of contacting points to be made by a single sensor. The extreme thinness of the sensor allows occlusion to be measured with little or no alteration of a patient's normal bite, and the high resolution provides detailed information to a dentist or other user about the interaction of dental surfaces. The sensor can simultaneously detect contacts at any electrode intersection. Thus the changing patterns of dental occlusion as a patient bites down on the sensor can be monitored to provide a total representation of the patient's occlusion as the jaw is closed.